1. Field of the Invention
The present invention relates to a technique for displaying color images using modulation panels.
2. Description of the Related Art
Projection-type display devices constitute a class of image display devices for displaying color images. In projection-type display devices, images are displayed based on a principle such that light emitted by an optical illumination system is modulated in accordance with a video signal by means of a liquid-crystal light bulb or other modulation panel, and the modulated light is projected onto a screen. The modulation panels are also referred to as xe2x80x9celectrooptical devicesxe2x80x9d because of the use of the electrooptical effect.
Color-enabled projection-type display devices often require three liquid-crystal light bulbs because of the need to modulate three-color (RGB) images. Fairly complex optical systems are needed, however, for projection type display devices having three liquid-crystal light bulbs. A demand therefore has existed in the past for a projection-type display device having a simpler structure. This demand is not limited to projection-type display devices and includes other color-image display devices featuring modulation panels.
Accordingly, an object of the present invention is to provide a color-image display device configured differently than in the past, and to provide a modulation panel therefor.
In order to attain at least part of the above and other objects of the present invention, there is provided an image display device for displaying color images. The image display device comprises: an optical illumination system is capable of emitting three-color illumination light including red light, green light, and blue light; an image display unit including a modulation panel having a plurality of pixels that allow illumination light emitted by the optical illumination system to be modulated in accordance with supplied drive signals; and a controller that controls the optical illumination system and the modulation panel. The modulation panel including for each pixel: a drive signal storage section that stores the drive signals corresponding to the three colors used for modulating individual components of the three-color illumination light; a color selection section that selects one of the drive signals stored in the drive signal storage section; and a modulation-executing section that performs modulation in accordance with the drive signal selected by the color selection section. The controller controls the lighting of the optical illumination system such that the modulation panel is illuminated with the three-color illumination light in a recurring fashion one color at a time, and controls the color selection section such that one of the drive signals stored in the drive signal storage section is applied to the modulation-executing section while being switched in synchronism with the lighting timing of the three-color illumination light.
With such an image display device, drive signals for three colors are stored in the drive signal storage section of each pixel, making it possible to display color images with a single-plate modulation panel by individually selecting these signals and feeding them to a modulation-executing section.
The drive signal storage section for each pixel may include: a first switching circuit connected to a data line for feeding the drive signals; a primary storage section that stores the drive signals fed to the first switching circuit; a second switching circuit connected to the output side of the primary storage section; and a secondary storage section connected to the color selection section and designed for storing the drive signals fed from the primary storage section via the second switching circuit.
With such a structure, the drive signals used in a subsequent modulation cycle can be stored in a primary storage section while modulation is performed in accordance with drive signals stored in a secondary storage section. It is therefore possible to reduce the need for shortening the time during which illumination light is on in order to transfer drive signals to each pixel, and to extend the period during which the illumination light is on. As a result, brighter color images can be obtained.
The data line may include three data lines for feeding the drive signals; and the first switching circuit may simultaneously transfer to the primary storage section the drive signals fed through the three data lines in a simultaneous and parallel fashion.
The structure and operation of the control section can thus be simplified by feeding the drive signals for the three colors in parallel to a single-plate modulation panel.
It is preferable that the second switching circuit is supplied with an on/off control signal common to all the pixels included in the modulation panel.
The drive signals of the three colors can thus be simultaneously transferred from the primary storage section to the secondary storage section for all the pixels on the single-plate modulation panel. As a result, the drive signals for performing the next modulation cycle can be easily accumulated in the secondary storage section.
It is preferable that the three-color illumination light is switched such that the illumination light of each color is selected N times (where N is a natural number) within a single vertical synchronization period and is caused to illuminate the single-plate modulation panel.
Images of all colors can thus be displayed in a balanced manner, making it possible to display highly balanced color images.
The present invention may be realized as an image display device, projection-type display device, modulation panel, electrooptical device, or other type of device.